In optical analyzing instruments, a sample to be analyzed is irradiated with light and the amount of light reflected from the sample is transmitted through the sample at narrow band wavelengths and is detected by a photodetector to provide an analog signal, which is converted to a digital value and fed to a computer for analysis by arithmetical operations. In some of these instruments, such as those manufactured by the Gardner/Neotec Division of Pacific Scientific Company, the assignee of this invention, the narrow band wavelength is swept through a range of values and, as the wavelength changes, the resulting analog signal value for each increment of change of wavelength is converted to a digital value and fed to the computer. The accuracy of the measurement at each wavelength can be increased by repeating the measurement cycle several times, that is, by causing the narrow band wavelength to be scanned through its range of values several times and averaging the resulting digital values obtained at each incremental wavelength during successive measurement cycles.
There has now become available an analog-to-digital converter which can convert analog values to digital values at a much higher rate than was heretofore possible, thus making it possible to sample the input analog signal at a higher rate.
However, in order to make use of the samples provided at this higher rate, a substantially more expensive digital computer would be required. In addition, a higher sampling rate would be required necessitating running the scanning equipment at a higher speed or a more expensive system to generate sampling pulses which determine the sampling interval.